Wireless technology uses radio frequency signals transmitted and propagated through space to communicate between separated nodes. Wireless technology, including wireless headsets, keyboards, pointing devices, etc., is ubiquitous in the commercial marketplace. Wireless internet access is now available in airports, conference rooms, and coffee shops. In the industrial controls marketplace, wireless sensor networks can be installed, reconfigured and maintained at only a fraction of the cost of more conventional wired networks.
Wireless sensors, wireless control devices, and wireless communication devices are being considered for aeronautical applications on commercial, private, and military aircraft in order to reduce the weight and to reduce the costs for designing, installing, manufacturing, testing, and certifying cable harnesses. Wireless sensors, wireless control devices, and wireless communication devices would also reduce the costs of aircraft interior and of system reconfiguration.
Conventional wireless technology, such as Bluetooth and IEEE 802.11, operates in the unlicensed Industrial, Scientific, and Medical (ISM) bands defined by the Federal Communications Commission (FCC). Members of the Aeronautical Vehicle Systems Institute (AVSI) believe that the Federal Aviation Administration (FAA) will not certify such equipment or specialized equipment operating in these unlicensed bands for use as sensors, controllers, or general communication devices in aircraft infrastructure.
Researchers are developing a wireless sensor network method and signal format that underlies the spectral bands currently dedicated for aeronautical use. Such an underlay approach could have the effect of greatly increasing the spectral efficiency of these dedicated aeronautical bands, as virtually all of the signals using those bands are legacy systems using single channel per carrier methods that are, in today's terms, relatively inefficient. Initial studies toward this end show some promise, however this approach will be subject to extreme scrutiny by the FAA to assure that no harmful interference to existing aeronautical radios is provided.
Cognitive radio is an emerging technology used to detect and avoid interference with current occupants of a given spectral region. With a cognitive radio, the radio itself surveys the available spectrum, characterizes the current use of that spectrum, and makes a decision about where and when to transmit based on an internal data base containing relevant regulatory policies. However, this type of cognitive radio technology has three significant drawbacks related to application to aeronautical wireless sensor networks. Firstly, cognitive radio access to spectrum is, by its very nature, statistical. The FAA has already indicated its dislike of statistical systems for safety critical applications. Therefore, cognitive access faces a high level of scrutiny and is likely to be denied. Secondly, cognitive radio requires access to some kind of master database or policy engine. While a centralized data base could be engineered and actually used via the wireless sensor network access itself, ensuring policy compliance throughout the distributed wireless sensor network on the aircraft is complex. This complexity is an additional barrier to certification approval by the FAA. Additionally, the spectral sensing capability increases the complexity of the wireless nodes. The success of wireless sensor networks rests on achieving the weight, maintenance, and reconfiguration advantages foreseen for the technology so that the nodes are very simple and very low cost. Even with the application of Moore's Law, cognitive nodes will always be more complicated than non-cognitive nodes.